Method for manufacturing surface acoustic wave device

ABSTRACT

A surface acoustic wave device which occupies a small mounting area and has a low profile, yet having an improved reliability, and can be made available at low cost. The surface acoustic wave device comprises a piezoelectric substrate, a function region formed of comb-like electrodes for exciting surface acoustic wave provided on a main surface of the piezoelectric substrate, a space formation member covering the function region, a plurality of bump electrodes provided on a main surface of the piezoelectric substrate and a terminal electrode provided opposed to the main surface of piezoelectric substrate. The bump electrode and the terminal electrode are having a direct electrical connection, and a space between piezoelectric substrate and terminal electrode is filled with resin. When the above-configured acoustic wave device is applied for a frequency filter, a resonator, in a portable telephone unit, a keyless entry or the like communication apparatus, the overall size of such apparatus can be reduced and a higher reliability is implemented.

This application is a divisional of U.S. patent application Ser. No.10/399,305, filed Aug. 15, 2003, now U.S. Pat. No. 6,969,945 which is aNational Phase of PCT/JP02/00949, filed Feb. 6, 2002.

TECHNICAL FIELD

The present invention relates to a surface acoustic wave device used asfrequency filter or resonator in a portable telephone unit, a keylessentry and the like communication devices. It also relates to a highfrequency module containing the surface acoustic wave device.

BACKGROUND ART

Portable telephone units and the like portable information terminalapparatus are making remarkable evolution towards the compactness insize, lightness in weight and slimness in overall contour. So, for thesemiconductor devices and other electronic components such as filter,resonator, etc., it is an essential requirement to be consistent withthe above trends if they are to be adopted in such recent apparatus.

An example of such components is disclosed in Japanese Patent Laid-OpenApplication No. H10-270975; a surface acoustic wave device, in which thesurface acoustic wave element is covered with an empty cover in thefunction region formed of comb-like electrodes, and is connected to aterminal electrode provided on the surface of wiring board by means ofbump, and a space between the surface acoustic wave element and thewiring board is filled with resin. Also, Japanese Patent Laid-OpenApplication No. 2000-323603 proposes a semiconductor device in which aterminal electrode is connected direct, eliminating a wiring board, witha bump formed on electrode pad of semiconductor device, and it is sealedwith resin excluding the bottom surface of terminal electrode.

In the following, some of the conventional surface acoustic wave devicesand the manufacturing method are described referring to the drawings.

FIG. 16( a) is a cross sectional view showing a first example ofconventional surface acoustic wave device. As shown in FIG. 16( a), apiezoelectric substrate 41 is provided on the surface with a functionregion 42 formed of comb-like electrodes for exciting surface acousticwave, and an electrode pad 43 for conveying electric signal to thefunction region 42. Each of the electrode pads 43 is connected withcorresponding terminal 44 of a package 46 via a thin metal wire 45. Thethin metal wire 45 is normally made of gold, aluminum, etc. Package 46in the present example is formed of laminated alumina ceramics 46 a, 46b, 46 c, and terminal 44 is electrically connected with terminalelectrode 48 via an inner electrode 47. Although not illustrated in thedrawing, piezoelectric substrate 41 is glued to the inside of package 46with a resin adhesive. Package 46 is hermetically sealed with a lid 49made of ceramic, metal, etc.

In the above-described first conventional example as shown in FIG. 16(a), however, a sufficiently large space needs to be secured in both thehorizontal and vertical directions for the operation of bonding the thinmetal wires 45, and respective electrode pads 43 as well as terminals 44are requested to have a certain area that is large enough for thebonding operation. These have been material factors that hindered thedevice downsizing. Furthermore, a parasitic inductance intrinsic to thinmetal wire 45 may deteriorate the high frequency characteristic of theelement. While on the production floor, thin metal wire 45 has to bebonded one by one to connect corresponding electrode pads 43 andterminals 44. This has blocked the cost cutting efforts substantially.

Addressing the above problems, a second example is proposed for aconventional surface acoustic wave device that enables furtherdownsizing, as shown in FIG. 16( b). In the proposed structure, asurface acoustic wave element 50 which is structured of a piezoelectricsubstrate 41, a function region 42 formed of comb-like electrodes, abump electrode 53 provided on electrode pad 52, etc. is mounted with theface down. The function region 42 is covered with a space formationmember 51 formed of a surrounding wall and a lid, so that a space forvibration is secured. A wiring board 54 is provided with a terminal 55on the surface, the surface acoustic wave element 50 is connected withterminal 55 via bump electrode 53. Terminal 55 and terminal electrode 56provided respectively on the upper surface and the bottom surface ofwiring board 54 are connected via an inner electrodes 57 which ispenetrating through the wiring board 54. A space between the surfaceacoustic wave element 50 and the wiring board 54 is filled with a resin58 in order to enhance fixing between the two.

In the structure of FIG. 16( b), however, contact location of bumpelectrode 53 and location of inner electrode 57 have to be shiftedsidewise to each other, since terminal 55 and terminal electrode 56disposed respectively on the upper surface and the bottom surface ofwiring board 54 are connected by inner electrode 57. Namely, because ofdifference in the curing/shrinking behavior between the base material ofwiring board 54 and the electrode paste of inner electrode 57, the innerelectrode 57 might protrude or sink in the thickness direction from thewiring board 54 during manufacturing.

In order to solve the above problem, a third example is proposed to aconventional structure, which enables to shrink the sidewise length too,as shown in FIG. 17( a).

Wiring board 54 is provided with a terminal electrode 56 which isstretching from the upper surface to the bottom surface covering theside face. Bump electrode 53 of surface acoustic wave element 50 isconnected to the terminal electrode 56. Surface acoustic wave element 50is provided with a space formation member 51 which secures a vibrationspace for function region 42, where surface acoustic wave excited on themain surface of piezoelectric substrate 41 propagates. Space between thesurface acoustic wave element 50 and the wiring board 54 is sealed witha resin 58.

The above-configured surface acoustic wave device is manufacturedthrough the following process steps. In the first place, a surfaceacoustic wave element 50 comprising a space formation member 51 coveringfunction region 42 and a bump electrode 53, and a wiring board 54comprising a terminal electrode 56 are prepared. These are coupledtogether with bump electrode 53 aligned on terminal electrode 56 andconnected to. Space between surface acoustic wave element 50 and wiringboard 54 is filled with a resin 58 for gluing the two together. Resin 58enhances the gluing strength and the reliability.

In the third example of conventional surface acoustic wave device asshown in FIG. 17( a), the main surface of surface acoustic wave element50 is sealed with resin 58, and size of the wiring board 54 can bereduced to approximately the same as that of surface acoustic waveelement 50. However, reduction in the thickness is limited by theexistence of a wiring board 54.

The downsizing and thickness-cutting race is proceeding rapidly alsoamong the semiconductor devices. For this purpose, a structure asillustrated in FIG. 17( b) is proposed. A semiconductor chip 59 isprovided with a bump electrode 61 formed on an electrode pad (notshown). A terminal electrode 62 is connected with the bump electrode 61.A first resin 63 is applied in a space between terminal electrode 62 andsemiconductor substrate 60 with the bottom surface of terminal electrode62 exposed. The back surface of semiconductor substrate 60 is coveredwith a second resin 64 for enhancing the strength and the reliability.

Process of manufacturing the above-configured semiconductor device isshown with cross sectional views in FIG. 18( a) through (e).

In the first place, a carrier 65 which is made of resin base filmprovided with a terminal electrode 62 formed thereon, and asemiconductor chip 59 provided with a bump electrode 61 formed onelectrode pad (not shown) of semiconductor substrate 60 are prepared asshown in FIG. 18( a). Then, these two are coupled together, asillustrated in FIG. 18( b), with the bump electrode 61 aligned on theterminal electrode 62 and connected by an ultrasonic thermal compressionprocess.

As shown in FIG. 18( c), a first resin 63 is applied surrounding thesemiconductor chip 59 and the bump electrode 61, and cured to provide anunder-fill. Then, as shown in FIG. 18( d), the carrier 65 is clampedfrom the up and down with an upper mold 66 and a lower mold 67, and aresin filling space 68 is filled with a second resin 64 to form asealing body. And then, it is taken out of the molds, and the carrier 65is removed. Thus, a semiconductor device protected in a chip-sizedpackage is provided as shown in FIG. 18( e); where it is protected by asealing body formed of first resin 63 and second resin 64, and terminalelectrode 62 is exposed in the bottom surface of the sealing body.

The above-configured structure and method of manufacturing seems to beapplicable also to manufacturing of a surface acoustic wave device.However, there are still a number of problems left to be solved beforeit is actually applied to the surface acoustic wave device.

For example, when a surface acoustic wave device is fabricated in thesame configuration as the above-described semiconductor device, theoverall thickness may be reduced by a thickness corresponding to theeliminated wiring substrate. But the outer edge of terminal electrode 62is disposed recessed from the side surface of thick sealing body ofresin. So, when mounting a surface acoustic wave device of the aboveconfiguration on a circuit board using a solder, a smooth solder flow isblocked by the very narrow gap between the bottom surface of sealingbody and the wiring board. As a result, accuracy in the height abovewiring board and the positioning accuracy of surface acoustic wavedevices may be dispersed by a dispersion in shape and area amongindividual lands formed on a wiring board and in quantity of dispensedsolder. Furthermore, due to the same reason as described above, bubblesin the molten solder are difficult to disappear during soldering on awiring board. This may cause voids in the solder.

Application of the above method for manufacturing semiconductor devicesas illustrated in FIG. 18( a) through FIG. 18( b) to the manufacture ofsurface acoustic wave devices further encounters following difficulty.Namely, since a resin base film is used for the carrier and each of theterminal electrodes is electrically independent, a surface acoustic waveelement might suffer from pyroelectric damage caused by heat appliedduring the production process, from the connection of bump electrode toterminal electrode up to the step of sealing.

DISCLOSURE OF INVENTION

The present invention addresses the above problems and aims to offer astructure that can implement a small-area and low-profile surfaceacoustic wave device, which device also implementing a reduced cost anda higher reliability. A method for manufacturing such devices is alsodisclosed. The present invention further offers an electronic circuitdevice incorporating such a surface acoustic wave device.

A first surface acoustic wave device in the present invention comprisesa piezoelectric substrate, comb-like electrodes provided on a mainsurface of the piezoelectric substrate for exciting surface acousticwave, a space formation member provided to cover the comb-like electrodeportion, a plurality of bump electrodes provided on the main surface ofpiezoelectric substrate, and a terminal electrode provided opposed tothe main surface of piezoelectric substrate. The bump electrode iselectrically connected direct to a main face of the terminal electrode,and at least a space between the piezoelectric substrate and theterminal electrode is filled with a resin.

A second surface acoustic wave device in the present invention is theabove first surface acoustic wave device further comprising a conductorisland which is disposed opposed to the space formation member.

A first method for manufacturing the surface acoustic wave device inaccordance with the present invention comprises the steps of disposingthe main surface of a surface acoustic wave element having a pluralityof comb-like electrodes for exciting surface acoustic wave, a spaceforming member for covering the comb-like electrode portion and a bumpelectrode provided thereon to be opposing to the main surface of acarrier having a terminal electrode formed thereon, and electricallyconnecting the bump electrode and the terminal electrode; filling aspace between the surface acoustic wave element and the carrier with aliquid state resin; and removing the carrier after the resin was cured.

A second method for manufacturing the surface acoustic wave device inaccordance with the present invention comprises the steps of preparing acarrier having a separation layer and a metal layer formed in the orderon the main surface, and selectively etching the metal layer to form aterminal electrode; connecting a bump electrode of surface acoustic waveelement with a terminal electrode; sealing with resin to cover thesurface acoustic wave element; peeling the carrier off; and cutting theresin and the terminal electrode to provide individual surface acousticwave devices.

A third method for manufacturing the surface acoustic wave device inaccordance with the present invention comprises the steps of forming aplurality of surface acoustic wave elements on a wafer made of apiezoelectric material; pressing the wafer onto the carrier; filling aspace between the wafer and the carrier with a sealing resin; removingthe carrier after the sealing resin was cured; forming a terminalelectrode so that part of it covers the bump electrode; and cutting thewafer and the sealing resin to provide individual surface acoustic wavedevices.

An electronic circuit device in accordance with the present inventioncomprises a surface acoustic wave device which comprises comb-likeelectrodes for exciting surface acoustic wave, an wall formedsurrounding the comb-like electrodes, a bump electrode and a terminalelectrode connected with the bump electrode, and is resin-sealedexposing the function region surrounded by the wall, which device ismounted on a wiring board having a land formed thereon and the terminalelectrode of the surface acoustic wave device is connected to the landof the wiring board.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a cross sectional view used to describe a first example ofsurface acoustic wave device in accordance with a first exemplaryembodiment of the present invention. FIG. 1( b) is the plan view, FIG.1( c) is the plan view showing the surface acoustic wave element.

FIG. 2( a), (b) are cross sectional views used to describe examples ofthe sealing with resin in a surface acoustic wave device in the firstembodiment.

FIG. 3( a) is a perspective view used to describe a second example ofsurface acoustic wave device in accordance with the first embodiment.FIG. 3( b) is the cross sectional view sectioned along the line A-B ofFIG. 3( a).

FIGS. 4( a), (b), (c) and (d) are cross sectional views used todescribe, respectively, a third, a fourth, a fifth and a sixth examplesof surface acoustic wave device in the first embodiment.

FIG. 5( a), (b) are cross sectional views used to describe,respectively, a first and a second examples in a second exemplaryembodiment.

FIG. 6( a)-(c) are cross sectional views showing the process steps, usedto describe a first example of method for manufacturing surface acousticwave devices in accordance with a third embodiment of the presentinvention.

FIG. 7( a)-(d) are cross sectional views showing the process steps, usedto describe a second example of method for manufacturing surfaceacoustic wave devices in accordance with a third embodiment of thepresent invention.

FIG. 8( a)-(f) are cross sectional views showing the process steps, usedto describe a first example of method for manufacturing surface acousticwave devices in accordance with a fourth embodiment of the presentinvention.

FIG. 9( a)-(d) are cross sectional views showing the process steps, usedto describe a second example of method for manufacturing surfaceacoustic wave devices in accordance with a fourth embodiment of thepresent invention.

FIG. 10( a)-(e) are cross sectional views showing the process steps,used to describe a third example of method for manufacturing surfaceacoustic wave devices in accordance with a fourth embodiment of thepresent invention.

FIG. 11( a)-(e) are cross sectional views showing the process steps,used to describe a fourth example of method for manufacturing surfaceacoustic wave devices in accordance with a fourth embodiment of thepresent invention.

FIG. 12( a), (b) are perspective views, used to describe an example offorming terminal electrodes in the manufacturing method in accordancewith a fourth exemplary embodiment of the present invention.

FIG. 13( a)-(e) are cross sectional views showing the process steps,used to describe a first example of method for manufacturing surfaceacoustic wave devices in accordance with a fifth exemplary embodiment ofthe present invention.

FIG. 14( a)-(e) are cross sectional views showing the process steps,used to describe a second example of method for manufacturing surfaceacoustic wave devices in accordance with a fifth exemplary embodiment ofthe present invention.

FIG. 15( a) shows a cross sectional view of a surface acoustic waveelement used in an electronic circuit device in accordance with a sixthexemplary embodiment of the present invention. FIG. 15( b) shows a crosssectional view of the electronic circuit device.

FIG. 16( a) is a cross sectional view used to describe a first exampleof conventional surface acoustic wave device. FIG. 16( b) is a crosssectional view used to describe a second example of conventional surfaceacoustic wave device.

FIG. 17( a) is a cross sectional view used to describe a third exampleof conventional surface acoustic wave device. FIG. 17( b) is a crosssectional view used to describe an example of conventional semiconductordevice.

FIG. 18( a)-(e) are cross sectional views showing the process steps,used to describe an example of method for manufacturing conventionalsemiconductor device.

FIG. 19( a), (b) are drawings used to describe the angle of sawing asingle crystalline piezoelectric wafer.

BEST MODE FOR CARRYING OUT THE INVENTION

Exemplary embodiments of the present invention are described in thefollowing referring to the drawings.

EMBODIMENT 1

A first example of surface acoustic wave device in accordance with afirst exemplary embodiment of the present invention is described withreference to the drawings.

FIG. 1( a) is a cross sectional view used to describe a first example ofsurface acoustic wave device in accordance with a first exemplaryembodiment of the present invention, FIG. 1( b) shows the device asviewed from the above, FIG. 1( c) is a drawing used to describe thesurface acoustic wave element.

Size of a piezoelectric substrate 1 is 1.5×1.0 mm, and 0.3 mm thick. Theterminology size used here means two-dimensional area of a device, andthe same applies also to the other embodiments and examples. As to thematerial of the piezoelectric substrate 1, a single crystallinepiezoelectric material such as lithium tantalate, lithium niobate,quartz, potassium niobate, langasite, etc. is used. Or a certainspecific substrate provided with film of zinc oxide, aluminum nitride,etc. formed thereon may be used. In the present embodiment, a lithiumtantalate sawn at Y 36° is used. The sawing angle is described referringto FIG. 19. FIG. 19( a) shows a state of single crystallinepiezoelectric material before sawing, illustrated in terms of the x, yand z axes. The single crystalline piezoelectric material isspontaneously polarized in the c axis direction, or z axis. A lithiumtantalate of y 36°, for example, is provided through a processing asillustrated in FIG. 19( b); revolving the y axis by 36° around the xaxis making it a new y′ axis, the z axis is also revolved by 36° makingit a new z′ axis, and it is sawn being regulated by the y′ axis. Asawing angle may be selected according to an intended devicecharacteristic; for most of the high frequency filters, a lithiumtantalate substrate sawn at the neighborhood of y 36° is used.

On the piezoelectric substrate 1, a comb-like electrodes 8 are providedfor exciting surface acoustic wave. Although a comb-like electrodeillustrated in FIG. 1( c) has only three teeth, there are more thanseveral tens of teeth in an actual electrode and the teeth of otherelectrode are disposed alternately. Although only two couples ofcomb-like filters are shown in FIG. 1( c), actual surface acoustic waveelement normally has several couples for forming a filter device, etc.An electrode pad 7 (not shown in FIG. 1( a), a cross sectional view)formed on piezoelectric substrate 1 is provided with a bump electrode 4.The bump electrode 4 can be made of any one of conductive materials;gold, solder, copper, tin, lead, silver, etc. are often selected.Normally, a metal containing at least one content among the above: groupis used.

Referring to FIG. 1( a), a function region 2 of surface acoustic waveelement represents an area in which the surface acoustic wave disperses,or an area where the comb-like filters are disposed. In order to protectthe function region 2, a space formation member 3 formed of an wall 3 aand a lid 3 b is provided by means of dry film resist, etc. Spacebetween piezoelectric substrate 1 and terminal electrode 5 is 60 μm inthe present embodiment.

Terminal electrode 5 is electrically connected with bump electrode 4 tofunction as the electrode for taking in and out electric signals. Aresin 6 is provided to fill the space between piezoelectric substrate 1and terminal electrode 5. As illustrated in FIG. 1( b), the resin 6 isdisposed around the circumference of piezoelectric substrate 1.

The above-configured first example of surface acoustic wave device inembodiment 1 has the following advantages.

Because a wiring board has been eliminated, device height can be furtherreduced from that of the conventional devices. Since bump electrode 4and terminal electrode 5 are connected direct on a straight line,element size can be made more compact and lower in the height. Sinceresin 6 is thin and less in volume, warping of surface acoustic wavedevice due to the shrinkage during curing and the thermal stress aftercuring, which being a task to be solved with conventional devices, canbe reduced significantly. As a result, it can be mounted on othercircuit board (secondary mounting) easily by means of reflow soldering,etc., and the reliability improves.

By the same reasons, residual stress at joint portion between electrodepad 7 and bump electrode 4, and that between bump electrode 4 andterminal electrode 5 can be reduced. This improves the withstandingcapability in thermal shock test, drop test, etc. Thus the reliabilityafter secondary mounting significantly improves.

As to the sealing with resin, one possible structure is shown in FIG. 2(a); where a space between piezoelectric substrate 1 and terminalelectrode 5 is sealed with a resin 6, and then the sides and the backsurface of piezoelectric substrate 1 are covered with a second resin 9.Another possibility is shown in FIG. 2( b); where it is entirely coveredwith a sealing resin 10, with the terminal electrode 5 exposed from thebottom surface of the sealing resin. The resin-sealed structurealleviates a drop-shock, and because of an increased overall thermalcapacitance it prevents a pyroelectric damage due to wild temperatureshift. Furthermore, the resin material covering entire piezoelectricsubstrate 1 alleviates warping of a surface acoustic wave device. Thiscontributes to lower the reject at secondary mounting.

Next, a second example of surface acoustic wave device in embodiment 1is described referring to the drawings.

FIG. 3( a) is a perspective view of second example of surface acousticwave device in embodiment 1, FIG. 3( b) is a cross sectional view of thesurface acoustic wave device of FIG. 1( a) sectioned along the line A-B.

FIG. 3( a) shows a perspective view of the bottom surface of sealingresin observed from an oblique direction, the upper surface of thesealing resin is hidden in the other side of the drawing. The reverseface 5 a of terminal electrodes 5 is exposed flush with the bottomsurface 10 a of sealing resin, while the side face 5 b is exposed flushwith the side surface 10 b of sealing resin.

As shown in FIG. 3( b), a cross sectional view, a surface acoustic waveelement is provided with a space formation member 3 which coversfunction region 2 of piezoelectric substrate 1, and a bump electrode 4is provided on an electrode pad.

When a surface acoustic wave device whose terminal electrode at sideface 5 b is exposed flush with the side surface 10 b of sealing resin issecondary-mounted, the side face 5 b, not only the bottom face 5 a, alsobecomes wet with solder expediting the solder flow. This contributes tomake the solder thickness after processing even, and the height ofsurface acoustic wave device after mounting even. By the same reasons,void in the solder as well as defective connection are reduced.

A third example which represents an improvement made on the secondexample in embodiment 1 is described referring to FIG. 4( a), a crosssectional view. The side face 5 b of terminal electrode in the presentthird example is flush with the side surface 10 b of sealing resin, butthe bottom face 5 a of terminal electrode is not flush with the bottomsurface 10 a of sealing resin. Namely, as shown in FIG. 4( a), theterminal electrode 5 is disposed in a hollow portion 11 of sealingresin. When such a surface acoustic wave device is secondary-mounted ona circuit board, mounting height of surface acoustic wave devices iskept at a certain fixed level, and there is no difficulty in thesoldering connection because the side face 5 b of terminal electrode isexposed in the side surface 10 b of sealing resin. Furthermore, becauseof the terminal electrode 5 disposed in a hollow portion of resin, theheight after secondary mounting can be suppressed to be lower than thatwith a device shown in FIG. 4( b).

A fourth example in embodiment 1 is described referring to FIG. 4( b), across sectional view. Although terminal electrode of the fourth exampleat the side face 5 b is flush with the side surface 10 b of sealingresin, the bottom face 5 a is protruding from the bottom surface 10 a ofsealing resin. The protruding bottom face 5 a facilitates fluent flow ofsolder when secondary-mounting the device on a circuit board, whichcontributes to make the device height after mounting even and solderingconnection more reliable. However, in a case where it opts for a lowerheight after secondary mounting, the earlier-described structure of FIG.4( a) is more preferred.

A fifth example in embodiment 1 is described referring to FIG. 4( c), across sectional view. The terminal electrode 5 has a thinner portion anda thicker portion 12 (hereinafter referred to as protruding portion ofterminal electrode), and bump electrode 4 is connected to the thinnerportion of terminal electrode 5. Bottom face 5 a of terminal electrodeis flush with bottom surface 10 a of sealing resin, and side face 5 b ofprotruding portion 12 of terminal electrode is flush with side surface10 b of sealing resin.

In the above-configured surface acoustic wave device, the protrudingportion 12 of terminal electrode brings about a greater contact areabetween terminal electrode 5 and sealing resin 10, resulting in anincreased terminal strength. Furthermore, since the side face 5 b ofprotruding portion 12 of terminal electrode is flush with side surface10 b of sealing resin, solder during secondary mounting can flow up tothis portion, which contributes to make height of devices after mountingstill more even. Still further, an enlarged area of protruding portion12 of terminal electrode exposed in the side surface 10 b of sealingresin enhances strength of the terminal accordingly.

A sixth example in embodiment 1 is described referring to FIG. 4( d), across sectional view. The structure of sixth example is a combination ofthe third example shown in FIG. 4( a) and the fifth example shown inFIG. 4( c). Advantages in the respective examples are integrallyimplemented. What is significant among the advantages is in the loweringof the device height after secondary mounting. This is because aclearance between the bottom surface 10 a of sealing resin and circuitboard can be readily reduced, since a superfluous solder at secondarymounting can escape to the side face 5 b. Furthermore, since the effortsfor precisely controlling the amount of cream solder to be printed on acircuit board can be alleviated, it offers another advantage also in thecost reduction and yield rate improvement during production.

In the above-described examples from the second through the sixth inembodiment 1, the space formation member 3 for protecting functionregion 2, viz. an area of comb-like electrodes, on piezoelectricsubstrate 1, is formed of an wall 3 a and a lid 3 b. The bottom face 5 aof terminal electrode is disposed flush with bottom surface 10 a ofsealing resin, or disposed hollowed therefrom. Therefore, a spacebetween circuit board and surface acoustic wave device after secondarymounting can be made smaller to a still lowered height. Furthermore, ina case where a circuit board is resin-molded after secondary mounting,the withstanding capability in a reflow test which is conducted insuccession to a moisture absorption test (hereinafter referred to asmoisture-absorption reflow test) improves because of the small clearancebetween circuit board and surface acoustic wave device. Thus the devicereliability improves. The secondary mounting can be made on either astandard printed board used in portable telephone unit, etc. or aspecific substrate mounted with a certain specific element. An exampleof the latter case is; a semiconductor device, or the like electroniccomponent, mounted on the surface of an element of laminated ceramicfilter.

There is another case in which a circuit board is provided with aterminal, and the entirety is used as a component; which is so-called ahigh frequency module. Such module can be downsized and low-profiledwhen a compact and low-profiled surface acoustic wave device in thepresent embodiment is used therein.

EMBODIMENT 2

A first example of surface acoustic wave device in accordance with asecond exemplary embodiment of the present invention is describedreferring to FIG. 5( a).

The first example shown in FIG. 5( a) uses a surface acoustic waveelement, which comprises a piezoelectric substrate 1 provided with afunction region 2, a space formation member 3 covering the functionregion 2, and a bump electrode 4 provided on the main surface; the bumpelectrode 4 is electrically connected with the terminal electrode, andthe entire structure is sealed with a sealing resin 10. In addition, aconductor island 13 is provided corresponding to the function region 2.Thus, a thin and compact surface acoustic wave device having theabove-described structure where the surface acoustic wave element isbuilt in and the function region 2 is protected with respect toelectro-magnetic property and reliability by the conductor island 13 isimplemented.

That it is “protected with respect to electromagnetic property” meansthat the function region 2 of surface acoustic wave device is wellshielded from the electromagnetic fields. In a case where a surfaceacoustic wave device is used in UHF or a higher band zone, or where itis mounted mixed with other high frequency device to form e.g. a highfrequency module, the advantage becomes more significant, among othercases.

That it is “protected with respect to reliability” means that thecomb-like electrode for exciting surface acoustic wave and the leadelectrode, pad electrode, etc. for inputting/outputting electric signalsto the comb-like electrodes are well protected against corrosion thatcould be caused by humidity, or other item, sneaking into the functionregion 2. Although mechanism of the corrosion has not been thoroughlyclarified yet, supposed reasons include a metal corrosion due todifference in the ionization tendency with hydrogen ion contained ininvading water content, and a galvanic corrosion due to difference inthe potential between a main material of the comb-like electrode, e.g.aluminum and other metal material. The other metal material can becopper, which has been alloyed with aluminum used as the main materialfor the comb-like electrode. In some practical cases, comb-likeelectrode is made of aluminum mixed with copper by a 0.5—several % forenhancing the anti-migration property. For the same purpose, titanium orthe like material is sometimes used. If gold or the like metal having ahigher potential than aluminum is used for an electrode pad, thegalvanic corrosion becomes significant. If sealing resin 10 or spaceformation member 3 contains an erosive halide or the like impurities, itwill be ionized by humidity in the air and existing in the functionregion of a surface acoustic wave device. This further expedites theabove-described process of corrosion. If sealing resin 10 or spaceformation member 3 contains an organic acid or the like acidic materialas the impurities, such material is be likewise existing in the functionregion. This provides an acidic environment in the function region toexpedite the process of corrosion. Besides the above-described, it isalso possible that the impurities intrude in the function region of asurface acoustic wave device at the production floor, and still existingeven after the device is completed. It also expedites the process ofcorrosion. Water normally sneaks into the function region in a gaseousstate, but it can turn into liquid by dew condensation. In this case,the corrosion becomes more significant. In order to alleviate thecorrosion, the length of moisture path should be made as long aspossible and the cross sectional area should be made as small aspossible. A conductor island 13 is provided in the present embodiment ata place corresponding to the lid 3 b, which place of lid forming thegreatest cross sectional area at the shortest length for the moisturepath. Thus, a surface acoustic wave device that is protected withrespect to the reliability is implemented. In a surface acoustic wavedevice of FIG. 5( a), wall 3 a and lid 3 b, which being constituents ofthe space formation member 3, may be glued to the conductor island 13with an adhesive agent, or by means of sealing resin 10.

Next, a second example in embodiment 2 is described referring to FIG. 5(b).

Description is made only on point of difference from the first exampleof FIG. 5( a). The space formation member 3 for covering function region2 in the second example is formed of a wall 3 a and a conductor island 3b, as shown in FIG. 5( b). The wall 3 a and the conductor island 13 maybe attached together either by means of compressive adhesion or with anadhesive agent. In whichever case, the overall thickness can be reducedwithout sacrificing the reliability.

In both of the first and the second examples in embodiment 2, it ispreferred that the terminal electrode at the side face 5 b is flush withthe side surface 10 b of sealing resin. However, the bottom face 5 a ofterminal electrode 5 may either be flush with sealing resin 10,hollowed, or protruded therefrom. The terminal electrode 5 may assume ashape in which there is a protruding portion 12 at a place outer thanthe place of connection with bump electrode 4.

Also the conductor island 13 should preferably be flush with terminalelectrode 5; and the conductor island 13 may be connected with at leastone of the terminal electrodes 5.

It is preferred that in both the embodiment 1 and embodiment 2, the humpelectrode 4 is made of a metal containing at least one among the groupof gold, tin, copper, lead and silver; while the terminal electrode 5and the conductor island 13 have a laminate structure formed of a layercontaining gold as the main ingredient and a layer formed of metalmaterial other than gold.

EMBODIMENT 3

A first example of method for manufacturing surface acoustic wave devicein accordance with a third exemplary embodiment of the present inventionis described referring to the drawings.

FIGS. 6( a) through (c) are cross sectional views showing the processsteps used to describe a first example of manufacturing method ofsurface acoustic wave device in accordance with the third embodiment ofthe present invention.

As shown in FIG. 6( a), a surface acoustic wave element is prepared,which element comprising a piezoelectric substrate 1 provided with afunction region 2 having comb-like electrodes, etc., an electrode pad(not shown), and a bump electrode 4 formed on the surface, the functionregion 2 being covered with a space formation member 3.

The comb-like electrode and the electrode pad of surface acoustic waveelement are formed by a sputtering process and a photolithography. Thecomb-like electrode is made with aluminum, or an aluminum alloy, e.g.copper aluminum alloy, copper aluminum scandium alloy.

The space formation member 3 is formed by an wall 3 a and a lid 3 b. Thewall 3 a is formed by first laminating a dry film resist and patterningit through photolithography, and then the lid 3 b by the same procedure.

The bump electrode 4 is formed by ball-bonding a gold wire on electrodepad and then pulling the wire off. Besides the above method, it can beformed also by a solder bump method, a method using solder ball, copperball, etc., or a plating process.

Next, as shown in FIG. 6( b), the bump electrode 4 is pressed on toterminal electrode 5 provided on a carrier 14 to be electricallyconnected together by means of ultrasonic wave. A resin 6 is appliedbetween the piezoelectric substrate 1 and a carrier 14, and cured.

Then, the carrier 14 is peeled off to complete a finished surfaceacoustic wave device as shown in FIG. 6( c). Although FIG. 6( c) showsonly a cross sectional view, the resin 6 is surrounding thecircumference of piezoelectric substrate 1. Although FIG. 6( c)illustrates an example in which the space formation member 3 is notcovered by resin 6, the entire bottom surface of piezoelectric substrate1 including the space formation member 3 may be covered with resin 6,excluding the bottom face of terminal electrode 5.

The carrier 14 having terminal electrodes 5 as shown in FIG. 6( b) ismanufactured as follows.

A metal layer of the same material for the terminal electrode, such ascopper, is formed covering the entire surface of carrier 14. Basicallythere is no limitation with respect to the material for carrier 14;copper, for example, may be used. A thin separation layer (not shown) isprovided between the metal layer and the carrier for easier peeling at alater stage. A resist pattern is formed on the metal layer with a placecorresponding to terminal electrode open. A plated layer of nickel, goldis formed by electrolytic plating, using the metal layer as anelectrode. After removing the resist pattern, the metal layer is etchedusing the plated layer as mask, and a terminal electrode 5 is completed.

When etching the metal layer, the peeling layer and part of carrier maybe etched at the same time. By so doing, the terminal electrode can bemade to be recessed from the resin surface applied in the surrounding.Thus a height difference in the step between bottom surface of terminalelectrode 5 and bottom surface of resin 6 can be controlled to beapproximately 5-50 μm, which makes a further contribution for reducingthe overall height.

Although the bump electrode and the terminal electrode in the presentfirst example are connected by ultrasonic means, the two items can beconnected together instead by heating if they are provided at respectivesurfaces with a metal layer that melts at heating. Furthermore, if thecarrier is made of a conductive material and the terminal electrode iselectrically connected with the carrier, electrode pads of a surfaceacoustic wave element get short-circuited when the element is mounted onthe carrier. This is advantageous in preventing an electrostaticdestruction and a pyroelectric damage on the production line.

Next, a second example of method of manufacturing surface acoustic wavedevice in accordance with a third exemplary embodiment of the presentinvention is described referring to FIGS. 7( a) through (d).

Referring to FIG. 7( a), a surface acoustic wave element is prepared,which element comprising a piezoelectric substrate 1 provided with afunction region 2, a space formation member 3 and a bump electrode 4formed on the main surface. The element is mounted on a carrier 14having no terminal electrode, and a sealing resin 10 is applied betweenpiezoelectric substrate 1 and carrier 14, and cured. And then, thesurface acoustic wave element sealed with sealing resin 10, shown inFIG. 7( c), is peeled off the carrier 14. It is essential that the tipend 15 of bump electrode 4 is exposed. Then, a terminal electrode 5 isformed connected with the bump electrode 4, as illustrated in FIG. 7(d).

The terminal electrode 5 can be formed by means of vacuum vapordeposition or a film forming process, or by printing a conductive resinand baking it.

In the description of the first and the second examples, a surfaceacoustic wave element is pressed on to the carrier and then resin 6 isapplied. Instead, the surface acoustic wave element or the carrier 14may be provided in advance with a resin 6 on the surface, and thencuring the resin 6 after the element and the carrier are connectedtogether.

EMBODIMENT 4

FIGS. 8( a) through (f) are cross sectional views showing the processsteps used to describe a first example of manufacturing method ofsurface acoustic wave device in accordance with a fourth embodiment ofthe present invention.

In the first place, a transference member is prepared by laminating aseparation layer 16 and a metal layer 17 on a carrier 14 at the mainsurface, as shown in FIG. 8( a).

A resist pattern 18 is formed on an area which eventually makes aterminal electrode, as shown in FIG. 8( b). The metal layer 17 is etchedoff using the resist pattern 18 as mask to provide a terminal electrode5. Resist pattern 18 is removed. As shown in FIG. 8( c), a surfaceacoustic wave element 19 is connected, with the bump electrode 4 on amain surface of terminal electrode 5. Then, as shown in FIG. 8( d), itis covered entirely with a sealing resin 10. Terminal electrode 5 andsealing resin 10 are peeled off at the separation layer 16, to obtain astructure as shown in FIG. 8( e).

Then, it is separated by cutting sealing resin 10 and terminal electrode5 along imaginary cut lines 20 shown in FIG. 8( e) indicated with dottedlines, to obtain individual surface acoustic wave devices shown in FIG.8( f). In this way, a surface acoustic wave device that has a terminalelectrode 5 flush with the bottom surface 10 a of sealing resin and theside face 5 b flush with the side surface 10 b of sealing resin isimplemented.

Next, a second example, which is an improvement of the first example inthe terminal electrode, is described referring to the drawings.

FIGS. 9( a) through (d) are cross sectional views showing the processsteps of the second example. Process steps after FIG. 9( d) remain thesame as those after FIG. 8( d).

As shown in FIG. 9( a), a transference member is prepared by laminatinga separation layer 16 and a metal layer 17 on the main surface of acarrier 14. A so-called reverse resist pattern 18 is formed on the mainsurface of metal layer 17, which resist having an opening in an areawhich eventually makes a terminal electrode.

As shown in FIG. 9( b), a plated layer 22 of gold or other material isprovided in the opening by using the resist pattern 18 as mask. Resistpattern 18 is removed, and then metal layer 17 is etched off using theplated layer 22 as mask. Thus a complex terminal electrode 24 formed ofa laminated body of metal layer 23 and plated layer 22, as shown in FIG.9( c). As to a material for the plated layer 22, it is preferred toselect such a material which is different from metal layer 17,separation layer 16 and carrier 14 in at least one item among theetchant and the etching rate.

As shown in FIG. 9( d), a surface acoustic wave element 19 is connected,with the bump electrode 4 on the complex terminal electrode 24. Theprocess steps after this remain the same as those shown in FIGS. 8( d)through (f).

In the present second example, the complex terminal electrode 24 isprovided with a plated layer 22 formed on the main surface. By selectinga metal that makes a good connection with the bump electrode 4 for theplated layer 22, reliability in the connection is improved.

Next, a third example, which is an improvement of the first example inthe terminal electrode, is described with reference to the drawings.

FIGS. 10( a) through (e) are cross sectional views showing the processsteps, used to describe the third example; steps after FIG. 10( e)remain the same as those after FIG. 8( d).

In the first place, a transference member is prepared by laminating aseparation layer 16 and a metal layer 17 on the main surface of acarrier 14, as shown in FIG. 10( a). On the metal layer 17, a resistpattern 18 is formed covering an area which eventually makes aprotruding portion of terminal electrode.

As shown in FIG. 10( b), the metal layer 17 is etched for a certaindepth from the upper surface using the resist pattern 18 as mask. Anarea which eventually makes the protruding portion 12 of terminalelectrode is thus formed. Resist pattern 18 is removed.

As shown in FIG. 10( c), a second resist pattern 25 having the shape ofterminal electrode is provided covering the protruding area either.Metal layer 17 is etched off using the second resist pattern 25 as mask,to form a terminal electrode 5 having protruding portion 12 as shown inFIG. 10( d).

A surface acoustic wave element 19 is connected, as shown in FIG. 10(e), with the bump electrode 4 on terminal electrode 5. The process stepsafter this remain the same as those shown in FIGS. 8( d) through (f).The cutting into individual devices is made at the protruding portion 12of terminal electrode.

Next, a fourth example, which is an improvement of the first example inthe terminal electrode, is described with reference to the drawings.

FIGS. 11( a) through (e) are cross sectional views showing the processsteps, used to described the fourth example; steps after FIG. 11( e)remain the same as those after FIG. 8( d).

In the first place, a transference member is prepared by laminating aseparation layer 16, a first meal layer 26 and a second metal layer 27on the main surface of carrier 14, as shown in FIG. 11( a). It ispreferred to select a material for first metal layer 26 and second metallayer 27, respectively, so that the layers are different to each otherin at least one item among the etchant and the etching rate. The etchantin the present context refers to an etching gas when etching isconducted with gas, or an etching liquid when etching is conductedthrough a wet etching process. A resist pattern 18 for providing aprotruding portion is formed on the second metal layer 27.

As shown in FIG. 11( b), the second metal layer 27 is etched off usingresist pattern 18 as mask, to provide a protruding portion 12. Resistpattern 18 is removed.

As shown in FIG. 11( c), a second resist pattern 25 having the shape ofterminal electrode is provided covering the protruding area 12. Thefirst metal layer 26 is etched off with the second resist pattern 25 asmask, to form a terminal electrode 5. Second resist pattern 25 isremoved to obtain the profile of FIG. 11( d).

A surface acoustic wave element 19 is connected, as shown in FIG. 11(e), with the bump electrode 4 on terminal electrode 5. The steps afterthis remain the same as those shown in FIGS. 8( d) through (f). It iscut at the protruding portion 12 of terminal electrode for separating itinto individual surface acoustic wave devices.

In the above-described examples 1 through 4, a conductor island asillustrated in FIG. 5( a) can be provided at the same time when theterminal electrode is formed. By providing a region for the conductorisland in the photo mask for forming terminal electrode, a conductorisland can be provided without modifying the current manufacturingprocedure. In this case, a lid 3 b of space formation member 3 is fixedto the conductor island by means of adhesive agent or sealing resin 10when mounting a surface acoustic wave element on carrier 14. In a casewhere the space formation member 3 is formed of wall 3 a alone, theattaching is made with an adhesive agent applied on at least one itemamong the top face of wall 3 a and the conductor island.

In the above-described examples 1 through 4, when a conductive materialis used for at least separation layer 16, individual terminal electrodesare connected in common by the separation layer 16; therefore, a surfaceacoustic wave element can be fully protected from the electrostaticdestruction or the pyroelectric damage at the production floor. Whenconductive material is used in both the separation layer 16 and thecarrier 14, the protection against electrostatic destruction andpyroelectric damage becomes to be further perfect. In practice,favorable results have been confirmed with, for example, a carrier 14made of copper foil, a separation layer 16 containing chromium or nickelas the main material, and a metal layer 17 and a second metal layer 27both made of copper foil.

In the above-described examples 1 through 4, if carrier 14 is slightlyetched at the surface during the process for forming terminalelectrodes, the surface acoustic wave device can be peeled off thecarrier more easily. This contributes to a higher production efficiencyand yield rate in the present manufacturing method. In this case,however, since the separation layer 16 underneath terminal electrode 5is made to be isolated, the separation layer 16 and the carrier 14 haveto be made of a conductive material in order to prevent theelectrostatic destruction and the pyroelectric damage.

Furthermore, in the above-described examples 1 through 4, one terminalelectrode among a group of terminal electrodes and other one amonganother group of terminal electrodes can be provided in a continuedarrangement, where an end of one terminal electrode continues to an endof other terminal electrode. A typical of such arrangement is shown inFIGS. 12( a) and (b).

FIG. 12( a) shows an example of carrier tape 14, on which a surfaceacoustic wave element is disposed and mounted in a certain specifiedarea. A region specified with imaginary cut lines 20 corresponds to anindividual resin sealed surface acoustic wave device. A first lead 28with a protruding portion 29 is a detached terminal electrode, while asecond lead 30 with a protruding portion 31 is that of continuedarrangement, where adjacent terminal electrodes are coupled together attheir protruding portion.

FIG. 12( b) is an imaginary view showing a state where a surfaceacoustic wave element is mounted on the carrier tape 14 at the certainspecified area shown in FIG. 12( a) and sealed with resin, and then itis cut into an individual device at the location of protruding portion.

When the devices are manufactured using terminal electrodes in acontinued state as described above, surface acoustic wave elements canbe disposed at a smaller interval. That the coupled lead is cut at themiddle to provide terminal electrodes contributes to eliminate the lossof materials.

EMBODIMENT 5

FIGS. 13( a) through (e) are cross sectional views showing the processsteps, used to describe a first example of manufacturing method ofsurface acoustic wave device in accordance with a fifth exemplaryembodiment of the present invention.

As shown in FIG. 13( a), a plurality of surface acoustic wave elementseach comprising a piezoelectric wafer 32 provided on the main surfacewith a function region 2, a space formation member 3 and a bumpelectrode 4 are prepared. The space formation member 3 for protectingfunction region 2 is provided by first forming an wall using a filmresist, and then forming a lid using a film resist.

Then, as shown in FIG. 13( b), bump electrode 4 of surface acoustic waveelement is pressed onto a carrier 14, and a sealing resin 33 is appliedin a space between wafer 32 and carrier 14, and cured.

Then, as shown in FIG. 13( c), carrier 14 is peeled off to have a tipend 15 of bump electrode 4 exposed. And then, as shown in FIG. 13( d), aterminal electrode 5 is formed, with part of it overlapping to bumpelectrode 4. At this stage, an isolated conductor island or a conductorisland coupled with a terminal electrode can be formed simultaneously.Next, terminal electrode 5, sealing resin 33 and wafer 32 are cut alonga cut line 20 to obtain an individual surface acoustic wave device asshown in FIG. 13( e).

Referring to the process step of FIG. 13( b), there is an alternativeprocedure which uses no carrier 14. That is, a sealing resin 33 isprovided on the main surface of a piezoelectric wafer 32, where a numberof surface acoustic wave elements have been formed, using a dispenser,or by means of spin-coating, and then the wafer is ground or polishedafter the sealing resin was cured until the tip end of bump electrode 4is exposed.

Terminal electrode 5 can be formed through the following processes.

After the processing is finished until the stage of FIG. 13( c), aconductive film is formed covering the whole surface of resin 33 by asputtering process, an ion plating process, an electron beam deposition,a deposition by resistive heating, etc. And then, a terminal electrode 5is formed by means of photolithography. For example, a photosensitiveresist layer is formed on the whole surface, which is exposed anddeveloped to a resist pattern. The conductive film is etched off usingthe resist pattern as mask, to provide a terminal electrode 5. Instead,a terminal electrode 5 can be provided direct; using a metal mask havingan opening in an area corresponding to terminal electrode when formingthe above-described conductive film on the wafer 32. In accordance withthe above procedure, the processing can be simplified and the productioncost can be lowered. Either one of the processes may be selected atoption, depending on the shape, size and requirement in the accuracylevel to be implemented with a terminal electrode 5. In the case ofpresent embodiment, a photolithography was used since the space betweenadjacent terminal electrodes is as small as 0.3 mm-0.4 mm.

The terminal electrode 5 can be formed instead by a plating process. Aphotosensitive dry film resist is laminated over the whole surface ofresin 33, and then the dry film resist is selectively removed for anarea of plating by means of photolithography. And then, copper or thelike material is plated after coring by palladium, etc. Nickel, gold,silver, tin, solder, etc. may be used for the plating, besides copper.Or some of these materials may be laminated. The point is that, theplating material facing to sealing resin 33 needs to have a goodfastening property with the sealing resin 33, so that it does not peeloff during and after secondary mounting. When a plated layer is formedin a multi-layered structure, the outermost layer can be selected amongthose materials having a high reliability with respect to secondarymounting. For example, when secondary mounting is performed by a reflowsoldering, it is preferred that the outermost material is selected fromamong the group of copper, gold, silver, tin, solder, etc., each ofwhich having a high wetting property with solder.

Still other alternative method is, first forming an underlayer by asputtering process, an ion plating process, an electron beam deposition,a deposition by resistive heating, an electroless plating method, etc.,and then applying further plating thereon. In this case, an electrolyticplating can be used, and the time needed for film formation can bereduced to a reduced manufacturing cost. Furthermore, the film thusformed has an increased intensity, which provides an enhanced blockingcapacity against water moisture, etc., leading to an improvedmoisture-proof property.

Still further, a terminal electrode 5 may be formed by applying aconductive resin by a printing process, and curing it. For example, ametal mask having an opening corresponding to terminal electrode 5 isplaced on the surface of sealing resin 33, and fixed thereon. Anappropriate quantity of conductive resin is applied on the metal maskand spread on the surface of sealing resin 33 by a squeegee, and thencured by heating after the metal mask is removed. As to metal materialcontained in the conductive resin, normally those having a high electricconductivity, for example, gold, silver, copper, palladium, platinum,aluminum, iron, nickel, or an alloy of these metals, or these metals ina laminate structure are selected. In a case where secondary mounting ismade by a reflow soldering, it is preferred to select a metal materialcontaining copper as the main component, in order not to have a terminalelectrode 5 eroded by solder and an electrically open state is caused.It is still more preferred if the copper is coated with gold or the likematerial that has a good wetting property with solder.

For the purpose of improving the electrical reliability in relation tobump electrode 4, thereby preventing the electrically off state, it ispreferred to provide a thin film as an underlayer, and then providing aconductive resin thereon. The underlayer can be formed by means of theearlier-described electron beam, vacuum deposition or sputtering byresistive heating, ion plating, etc. Also, a plating method can used.The underlayer is advantageous also in terms of anti-moisture property;it enhances the performance of blocking water moisture, etc.

A conductor island may of course be formed at the same time whenterminal electrode 5 is formed. Thus the above-described manufacturingmethod makes it possible to manufacture the surface acoustic wavedevices through an easy procedure at the wafer level, which devicesexhibiting superior properties in electromagnetic performance and interms of reliability. The cost can be reduced substantially.

Now in the following, a second example of manufacturing method ofsurface acoustic wave device in accordance with a fifth embodiment ofthe present invention is described referring to the drawings.

FIGS. 14( a) through (e) are cross sectional views showing the processsteps, used to describe the second example of manufacturing method ofsurface acoustic wave device in accordance with a fifth embodiment ofthe present invention.

As shown in FIG. 14( a), a number of surface acoustic wave elements areformed on the main surface of a piezoelectric wafer 32, which surfaceacoustic wave element comprising a function region 2, a space formationmember 3 and a bump electrode 4. The space formation member 3 forprotecting function region 2 is provided by first forming a wall bodyusing a film resist, and then a lid using a film resist.

As shown in FIG. 14( b), the bump electrode 4 of surface acoustic waveelement is pressed on a terminal electrode 5 formed on a carrier 14, andconnected.

As shown in FIG. 14( c), a space between wafer 32 and carrier 14 isfilled with a sealing resin 33, and cured.

As shown in FIG. 14( d), separation layer 16 and carrier 14 are peeledoff. And then, terminal electrode 5, sealing resin 33 and wafer 32 arecut along a cut line 20, to provide individual surface acoustic wavedevices as shown in FIG. 14( e).

Like in the earlier example, an isolated conductor island or that whichis electrically coupled with terminal electrode 5 may be formed on themain surface of carrier 14 at the same time when the terminal electrode5 is formed. In this case, the conductor island and space formationmember 3 may be attached together by means of adhesive agent or sealingresin 33. In a case where the space formation member 3 is formed of wallalone, the attaching is made with an adhesive agent applied on at leastone among the top face of wall and the conductor island. In this way,the manufacturing process can be simplified like in the first example,and compact and low-profile surface acoustic wave devices aremanufactured.

EMBODIMENT 6

An electronic circuit device in accordance with a sixth exemplaryembodiment of the present invention is described referring to thedrawings.

FIG. 15( a) shows a cross sectional view of a surface acoustic wavedevice used in an electronic circuit device in accordance with a sixthexemplary embodiment of the present invention. FIG. 15( b) is a crosssectional view of the electronic circuit device in the sixth embodiment.

As shown in FIG. 15( a), a surface acoustic wave device 34 used inembodiment 6 comprises a function region 2 provided with comb-likeelectrodes formed on the main surface of a piezoelectric substrate 1, anwall 3 a surrounding the function region 2, a bump electrode 4 and aterminal electrode 5. Space between piezoelectric substrate 1 andterminal electrode 5 is filled with a resin 6.

FIG. 15( b) shows a state of circuit board mounted with theabove-configured surface acoustic wave device.

A circuit board 35 is provided on both surfaces with wiring conductorlines (not shown) and lands 36 for components mounting. Terminalelectrode 5 of the surface acoustic wave device 34 is connected with theland 36.

Circuit board 35 can be a multi-layered substrate containing circuitcomponents formed within inside. Normally, the circuit board is mountedalso with electronic component 37 on the main surface. A surfaceacoustic wave device 34 may be covered with resin after it issecondary-mounted. Also a surface acoustic wave device provided with aspace formation member formed of an wall and a lid may be used.

Since height of the surface acoustic wave devices can be maintained at acertain determined level, the overall height of a finished electroniccircuit device can be controlled with ease to be within a certainspecification. Thus the electronic circuit device can be made to have alower profile.

INDUSTRIAL APPLICABILITY

As described in the above, a surface acoustic wave device in the presentinvention is made with a surface acoustic wave element comprising afunction region formed of comb-like electrodes, a space formation memberfor protecting the function region, a bump electrode and other items.The element is connected with a terminal electrode, and the key part issealed with resin. A device thus structured occupies a small mountingarea and implements a low device-profile. It can be offered at a lowcost, yet provides a high reliability.

Other surface acoustic wave device in the present invention has astructure in which the bottom face of terminal electrode is exposed inthe bottom surface of sealing resin, and the side face of terminalelectrode is flush with the side surface of sealing resin. Whensecondary-mounting the above-configured device on a circuit board,solder flows fluently, as a result the solder thickness after mountingis even. The solder can also flow to the side face of a terminalelectrode, therefore the soldered portion can be free from void ofsolder, to a high connection reliability. This advantage is furtherenhanced when the terminal electrode is made thicker at the outer face.

Other surface acoustic wave device in the present invention is providedwith a conductor island disposed opposed to the function region. This iseffective to protect the function region from a moisture intrusion, andthe reliability is improved. Furthermore, when a surface acoustic wavedevice having the conductor island is secondary-mounted, the conductorisland functions as electromagnetic shield to implement a circuit of lownoise and low redundant radiation. This advantage is further enhanced byconnecting the conductor island to the grounding level of the circuit.

A method for manufacturing surface acoustic wave device in the presentinvention uses a carrier provided with terminal electrode formedthereon, and comprises the steps of connecting a bump electrode ofsurface acoustic wave element with the terminal electrode, filling aspace between the surface acoustic wave element and the carrier with aresin and curing the resin, and removing the carrier. In accordance withthe manufacturing method, thin and small-sized surface acoustic wavedevices are made available with ease.

Other method for manufacturing surface acoustic wave device in thepresent invention uses a carrier provided with terminal electrode formedthereon, and comprises the steps of connecting a bump electrode ofsurface acoustic wave element with the terminal electrode, sealing thesurface acoustic wave element disposed on the carrier with resin andcuring the resin, and cutting the sealing resin and the terminalelectrode after removing the carrier. In accordance with themanufacturing method, it is easy to manufacture the surface acousticwave devices whose terminal electrode at the bottom face is exposed inthe bottom surface of sealing resin, while the side face of the terminalelectrode is flush with the side surface of sealing resin.

Other method for manufacturing surface acoustic wave device in thepresent invention comprises the steps of pressing a wafer having anumber of surface acoustic wave elements face to face onto a carrierhaving terminal electrodes and connecting these together, filling aspace between the wafer and the carrier with resin and curing the resin,and cutting the wafer, resin and terminal electrode. In accordance withthe manufacturing method, small and thin-profile surface acoustic wavedevices can be produced efficiently at a low cost.

1. A method for manufacturing surface acoustic wave device comprising: afirst step of opposing a main surface of said surface acoustic waveelement comprising a plurality of comb-like electrodes for excitingsurface acoustic wave, a space formation member covering each of saidcomb-like electrodes and a bump electrode to a main surface of a carrierprovided with a terminal electrode formed thereon, and making electricalconduction between said bump electrode and said terminal electrode; asecond step of filling a liquid-state resin between said surfaceacoustic wave element and said carrier; and a third step of removing thecarrier after said resin was cured.
 2. The method for manufacturingsurface acoustic wave device recited in claim 1, wherein said bumpelectrode and said terminal electrode are made to have electricalconduction by means of an ultrasonic connection.
 3. The method formanufacturing surface acoustic wave device recited in claim 2, whereinat least a portions of said bump electrode and said terminal electrodemaking contact with said bump electrode are made of gold, and the goldof said terminal electrode is provided by means of electrolytic plating.4. The method for manufacturing surface acoustic wave device recited inclaim 1, wherein said bump electrode and said terminal electrode aremade to have electrical conduction through connection by melting of ametal with heat.
 5. The method for manufacturing surface acoustic wavedevice recited in claim 1, wherein the carrier is a conductor.
 6. Themethod for manufacturing surface acoustic wave device recited in claim5, wherein said terminal electrode and the carrier are making electricalconduction.
 7. The method for manufacturing surface acoustic wave devicerecited in claim 1, wherein said third step comprises removing thecarrier after said resin was cured, so as to allow the terminalelectrode to expose from the cured resin.
 8. The method formanufacturing surface acoustic wave device recited in claim 1, whereinthe terminal electrode has a first surface and a second surface oppositeto the first surface of the terminal electrode, said first stepcomprises: opposing the main surface of said surface acoustic waveelement to the main surface of the carrier provided with the firstsurface of the terminal electrode thereon; and connecting the bumpelectrode to the first surface of the terminal electrode, and saidremoving of the carrier after said resin was cured, so as to allow theterminal electrode to expose from the cured resin comprises removing thecarrier after said resin was cured, so as to allow the first surface ofthe terminal electrode to expose from the cured resin.
 9. A method formanufacturing surface acoustic wave device comprising: a first step ofopposing a main surface of said surface acoustic wave element comprisinga plurality of comb-like electrodes for exciting surface acoustic wave,a space formation member covering each of said comb-like electrodes anda bump electrode to a main surface of a carrier provided with a terminalelectrode formed thereon, and making electrical conduction between saidbump electrode and said terminal electrode; a second step of filling aliquid-state resin between said surface acoustic wave element and saidcarrier; and a third step of removing the carrier after said resin wascured, wherein the carrier is a conductor.
 10. The method formanufacturing surface acoustic wave device recited in claim 9, whereinsaid bump electrode and said terminal electrode are made to haveelectrical conduction by means of an ultrasonic connection.
 11. Themethod for manufacturing surface acoustic wave device recited in claim10, wherein at least a portion of said bump electrode and said terminalelectrode making contact with said bump electrode are made of gold, andthe gold of said terminal electrode is provided by means of electrolyticplating.
 12. The method for manufacturing surface acoustic wave devicerecited in claim 9, wherein said bump electrode and said terminalelectrode are made to have electrical conduction through connection bymelting of a metal with heat.
 13. The method for manufacturing surfaceacoustic wave device recited in claim 9, wherein said terminal electrodeand the carrier are making electrical conduction.